Making Calls Using Keylock Bypass Bug on iOS 4.1

A keylock bypass bug has been found in iOS 4.1 which allows unauthorised users circumvent the passcode screen to make calls. It’s a pretty simply trick which involves entering a number (eg. 1) on the ‘Emergency Call’ screen, pressing Call and then immediately pressing the lock button. This brings up the Phone app where the user can pick a name from the contact list, or enter a phone number of their choice. To return the phone to normal (without rebooting it), just hold down the Home button until the Voice screen comes up, press Cancel, and then the lock button.

You are able to add/delete contacts, and open the Mail app by sharing a contact where you can then create and send emails.

Here’s a demo:

I’m running 3.1.3 on an iPhone 2G, and for some reason I can make arbitrary calls directly from the Emergency Call screen without any fancy tricks. Go figure.

These kinds of vulnerabilities are not unique to iPhones however, with similar bypass bugs being found in some Android-based phones.

[Update] Thanks Andy for clarifying what an attacker can do using this technique.

[Update 2] This bug has been fixed in the iOS 4.2 update.